TL (luminescent/fluorescent tube) lighting devices exist in different form factors, such as those called T12, T8, and T5, e.g. having different diameters where T5 has the smallest diameter. Large efforts have been spent on reconstructing the traditional fluorescent tube having a combined electrode-gas light emitter by means of LEDs (Light Emitting Diodes). This tubular lighting device is called LED TL lighting device, and it is a tube having the same form factor and typically the same electrical terminals as a corresponding traditional TL lighting device, but it is provided with LEDs as light emitters. Several LEDs are arranged on an elongate base member, along the length of the tube, in one or more rows or some other configuration. However, the diameter of a form factor T5 lighting device is small and complicates the LED mounting. Luminaires often offer some extra space in the direction of the light output, inviting the use of a larger form factor lighting device, but there is not enough mounting space to install such a larger form factor lighting device.
Additionally, a LED TL lighting device that uses the original form factor socket and a rewired driver of the luminaire is subject to some safety risks. There may be a risk of electrical shock if the LEDs or PCB traces can be touched by hand.
Also, it is possible that the LEDs are blue LEDs that may be too bright for direct on-looking; they should be operated only when there is no direct line of sight onto the LEDs, and all light is reflected or transmitted by a Remote Phosphor layer.